Dear Colleagues,

It is widely acknowledged that the deficiencies in ductility and tensile strength of plain concrete material yield numerous difficulties in engineering practice. Considerable attempts have been made over decades to improve the mechanical properties of concrete.

The state-of-the-art concrete modification technology indicates that the addition of fibers is an eco-friendly solution for enhancing the strength and ductility of concrete. Over the past few years, fiber-reinforced concrete (FRC) has been experiencing rapid development, and the application of FRC in modern concrete constructions has become widespread. Among the various types of FRC developed using different fiber types at multi-length scales, hybrid fiber technology, as a combination of high-strength macro metal fibers and high-elongation micro organic fibers, is regarded as a promising reinforcing method.

A number of research works have reported that the mechanical performance of concrete under complex stress states differs significantly from that under uniaxial load, where the yield strength, plastic deformation, and damage evolution show high sensitivity to confinement. Lateral confinement can remarkably limit the generation of damage and cracks in the material and thus improve its strength, ductility and energy dissipation performance.

However, previous research has mostly focused on the mechanical properties of FRC under uniaxial stress states. Therefore, experimental data demonstrating the mechanical properties of FRC under cyclic triaxial compression are still lacking. Moreover, few studies explain the failure mechanism and the internal physical and mechanical processes of FRC under triaxial loading process, which remains a topic of open debate in FRC research.

Meanwhile, with the development of computer technology, numerical simulation is providing a new method for concrete mechanical analysis. This method can overcome the disadvantages of actual testing by sparing the waste of resources and time consumption, and it allows the development of internal cracks inside the concrete to be monitored in real time and, thus, it becomes possible to identify whether the cracks are caused by tensile or shear failure. Hence, it has attracted great attention in academic circles.

On the other hand, the need for repair and rehabilitation of existing concrete structures is rising around the globe, in large part due to the vast built environment inherited from the 20th century, with continually reducing functionality. Moreover, recent constructions tend to deteriorate more rapidly under the negative influence of mechanical loads and current changes in the atmospheric conditions, increasing the need for early maintenance operations. These can come with additional economic burdens and safety concerns if suitable renovation and strengthening solutions are not applied. Thus, the development and widespread use of enabling technologies that can offer reliable and durable rehabilitation of built infrastructures constitutes an important challenge currently facing civil engineers.

The durability of conventional concrete can significantly decline when subjected to severe environments, due to the electrochemical corrosion of embedded reinforcement and/or the physical degradation of the concrete itself. Durability of concrete is considerably improved by the incorporation of SCMs. Due to pozzolanic activity and the filling effect, the use of SCMs can result in high-performance concrete having both enhanced mechanical characteristics and reduced permeability, which lead to improved durability.

Dr. Ping Duan
Guest Editor

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• fiber-reinforced concrete (FRC)
• high-performance concrete
• supplementary cementing materials (SCMs)
• alkali-activated concrete
• solid waste utilization